My ML430 is six years old. The day after I bought it the power steering messed up. It was a small annoying problem that was easily solved. I haven't had any other problems.
This is an overall great vehicle. The ride is very smooth, but fast.
I was impressed with the gadgets especially the stereo and speakers.
I bought it with 39000 miles. I drove it for a year now and I have no problems except brake pads which is 200 dollars.